sublimemediumRule

Attachment: HTML file contains exclusively Javascript

Attached HTML file does not contain any HTML other than a <script> block.

MITRE ATT&CK

T1566 T1566.001 T1566.002 T1598 T1204.002 T1486 T1036 T1027 T1059

defense-evasionexecution

Detection Query

type.inbound
and any(attachments,
        (
          .file_extension in~ ("html", "htm", "shtml", "dhtml")
          or .file_extension in~ $file_extensions_common_archives
          or .file_type == "html"
        )
        and any(file.explode(.),
                length(.scan.strings.strings) == 1
                and any(.scan.strings.strings,
                        regex.imatch(., '\s{0,}<script.*')
                )
                and any(.scan.strings.strings,
                        strings.ends_with(., "</script>")
                )
        )
)

Data Sources

Email MessagesEmail HeadersEmail Attachments

Platforms

Raw Content

name: "Attachment: HTML file contains exclusively Javascript"
description: |
  Attached HTML file does not contain any HTML other than a <script> block.
type: "rule"
severity: "medium"
source: |
  type.inbound
  and any(attachments,
          (
            .file_extension in~ ("html", "htm", "shtml", "dhtml")
            or .file_extension in~ $file_extensions_common_archives
            or .file_type == "html"
          )
          and any(file.explode(.),
                  length(.scan.strings.strings) == 1
                  and any(.scan.strings.strings,
                          regex.imatch(., '\s{0,}<script.*')
                  )
                  and any(.scan.strings.strings,
                          strings.ends_with(., "</script>")
                  )
          )
  )
attack_types:
  - "Credential Phishing"
  - "Malware/Ransomware"
tactics_and_techniques:
  - "Evasion"
  - "HTML smuggling"
  - "Scripting"
detection_methods:
  - "Archive analysis"
  - "File analysis"
id: "b6d38168-20bb-5550-8843-6af9426af8b1"